1. Field of the Invention
This invention relates generally to assembly construction of shaft seal devices. This invention relates especially but not exclusively to the assembly construction of such shaft seal devices for use with a stirrer or the like providing for a seal of a stirred fluid under a high pressure or extremely high pressure.
2. Description of the Related Art
A shaft seal device as a relative art of the present invention is illustrated in FIG. 3. FIG. 3 is a half cross-sectional view of a high pressure mechanical seal device.
In FIG. 3, a rotary shaft 175 is supported in a rotary movable manner by a bearing portion, not shown in the figure, which is disposed in a housing 151 of the stirrer 150. The rotary shaft 175 extends throughout the inside and the outside of the housing 151. The inside of the stirrer 150 is filled with a high pressure sealing fluid A.
The housing 151 through which the rotary shaft 175 extends is divided into three chambers 152A, 152B and 152C. The chamber 152 comprises, counted from the sealing fluid A side, a first chamber 152A, a second chamber 152B and a third chamber 152C.
When the pressure of the sealing fluid A is 20 MPa say, a pressure fluid of 15 MPa which is a little lower than that of the fluid A is supplied to the first chamber 152A from a first pipe 153A.
Similarly, a pressure fluid of 10 MPa which is further lower than the pressure of the first chamber 152A is supplied to the second chamber 152B from a second pipe 153B.
Likewise, a pressure fluid of 5 MPa which is yet lower than the pressure of the second chamber 152B is supplied to the third chamber 152C from a third pipe 153C. Therefore, a plurality of chambers 152A, 152B, 152C are disposed in such a manner that the high pressure of the sealing fluid A is decreased step by step.
Without such a means, a high pressure directly acts on a first mechanical seal device 110 and may cause a damage to the device 110.
The first chamber 152A, second chamber 152B and third chamber 152C contain respective mechanical seal devices 110, 120, 130 inside, and these mechanical seal devices 110, 120, 130 are referred to, from the sealing fluid A side towards the atmospheric region, a first mechanical seal 110, a second mechanical seal 120 and a third mechanical seal 130, respectively.
The first mechanical seal 110 is a high pressure mechanical seal due to a high pressure nature of the sealing fluid A. Likewise, high pressure mechanical seals are used for the second mechanical seal 130 as well as the third mechanical seal 120 in accordance with a level of the pressure to which they are subjected.
Sealing fluid A used in a stirrer 150, in general, undergoes a high pressure, and mechanical seal devices 110, 120, 130 are typically employed because elastic rubber seals cannot sustain such a high pressure.
These mechanical seals 110, 120, 130 are specifically prepared for such a high pressure, and they are mounted in such a way that a shaft sleeve 111 is fitted over the rotary shaft 175 via an O-ring. A spring support 112 engages the sleeve 111 at the shoulder part of the sleeve 111, and a rotary seal ring 113 is fitted to the other end of the sleeve 111 in a movable manner via an O-ring. A biasing spring 114 supported by the spring support 112 is disposed to exert an urging force to the rotary seal ring 113.
On the other hand, a stationary seal ring 115 is fitted to a retaining portion of the housing 151 via an O-ring which has an opposing seal face making a sealing contact with the slidable seal face of the rotary seal ring 113.
The second mechanical seal 120 and the third mechanical seal 130 are constructed in a similar manner to the first mechanical seal 110 although some symbols are omitted in the figure.
The first mechanical seal 110 effectively seals the high pressure sealing fluid A within the stirrer in cooperation with the fluid pressure within the first chamber 152A which is a little lower than the pressure of the fluid A.
Likewise for the second mechanical seal 120, it seals the pressure fluid within the first chamber 152A in cooperation with the fluid pressure within the second chamber 152B which is two-step lower than the pressure of the fluid A.
Similarly, the third mechanical seal 130, it seals the pressure fluid within the first chamber 152B in cooperation with the fluid pressure within the second chamber 152C which is three-step lower than the pressure of the fluid A.
Use of such pressure resistive mechanical seals, which reduce the fluid pressure in a stepwise manner from chamber to chamber, is essential to provide a secure seal for the sealing fluid A under a high pressure. In other words, when sealing a high pressure fluid, without a plurality of mechanical seals gradually reducing the high pressure in multiple steps, a single mechanical seal device cannot sustain such a high fluid pressure and will be worn out or damaged at its early stage.
In such a multiple step mechanical seal device 100, the inner diameter of step shoulders 151A, 151B, 151C, which receive the stationary seal rings 115, is formed larger than any of the outer diameters of the stationary seal rings 115, the rotary seal ring 113 and the spring support 112. Thus, it will be difficult to dispose the mechanical seals 110, 120, 130 in the respective chambers 152A, 152B, 152C as illustrated in FIG. 3.
Therefore, disposition of the mechanical seals 110, 120, 130 requires the housing 151 to be split into two pieces along the axial direction relative to the rotary shaft 175, and the mechanical seals 110, 120, 130 need to be assembled by being inserted along the axial direction relative to the rotary shaft 175 in order for the seals to be disposed in respective chambers 152A, 152B, 152C.
However, splitting the housing 151 along the axial direction relative to the rotary shaft 175 prevents O-rings or the like from being used and sealing of the split faces will be made difficult. In case of sealing a high pressure seal fluid, in particular, the high fluid pressure creates an undesirable gap between the split faces.
Furthermore, splitting the housing 151 axially makes it difficult to align the stationary seal ring 115 with respect to the rotary seal shaft 175. This will cause a trouble to the seal performance of the stationary seal ring 115. In particular, the more mechanical seals 110, 120, 130 are involved to reduce the pressure, the more serious these troubles become likely.
Use of such multi-step mechanical seals 110, 120, 130 will result in a high production cost due to difficulties in their fabrication process as well as the assembly process.
The present invention is introduced to resolve the above mentioned problems. A primary technical goal which this invention tries to achieve is to provide a mechanical seal device at a reasonable cost while avoiding a total cost increase of a shaft seal device which is caused by employing a plurality of expensive mechanical seals.
Another goal for the present invention is to reduce an assembly cost of the shaft seal device.
Sealing a high pressure fluid by means of a plurality of seal devices will lead to a large construction because of requirement of many chambers to retain them. Therefore, yet another goal of the present invention is to reduce the size of the shaft seal device by making the installation space compact.
A primary object of the present invention is to resolve the above mentioned technical problems, and a solution to such problems is embodied as follows.
A preferred shaft seal device in accordance with the principles of the present first invention is a shaft seal device for providing a seal against a process fluid between a housing and a rotary shaft, the shaft seal device comprising:
a first seal portion which is located within the device and comprises a stationary seal ring retained in the housing and a rotary seal ring making a sealing contact with the stationary seal ring;
a first sleeve which has a large diameter surface by which the rotary seal ring is retained;
a second sleeve which retains a large diameter surface and is located on the opposite side of the process fluid relative to the first sleeve;
a second seal portion which comprises a rotary seal ring retained in the large diameter surface of the second sleeve and a stationary seal ring making a sealing contact with the rotary seal ring;
a fixed sleeve which retains an outer diameter surface and an inner diameter in which the outer diameter surface is fitted with the inner diameter surface of the first sleeve and the second sleeve and the inner diameter surface is fitted over the rotary shaft; and
a connecting means which is disposed, respectively, in the fixed sleeve and the second sleeve by which the two sleeves are joined with each other.
In the shaft seal device of the first invention related to the preferred embodiment, the first seal portion is installed on the fit surface between the first sleeve and the first housing, and the first sleeve is fitted to the fixed sleeve.
Next, the second sleeve is fitted to and joined with the fixed sleeve after mounting the second seal portion between the second sleeve and the second housing. Thus, the first sleeve and the second sleeve are retained via the fixed sleeve, and the first seal portion and the second seal portion are assembled between the individual sleeves and the housings to be integrated as a whole unit of shaft seal device. The inner diameter surface of the fixed sleeve is further fitted to the rotary shaft to complete the assembly of the shaft seal device onto the machine apparatus. Therefore, the assembly process as a whole is very simple and its assembly cost will be decreased.
When the shaft seal device needs to be disassembled in case of a trouble, a repair work or the like, loosening and disengaging the connecting means will separate the first seal portion and the second seal portion. Also being able to simplify a mounting construction of the first seal portion and the second seal portion will simplify a design process for the seal device.
A preferred shaft seal device in accordance with the principles of the present second invention is a shaft seal device for providing a seal against a process fluid between a housing and a rotary shaft, the shaft seal device comprising:
a first seal portion being located inwardly relative to an apparatus which contains a fluid and comprising a stationary seal ring retained in the housing and a rotary seal ring for making a sealing engagement relative to the rotary seal ring;
a first sleeve having a large diameter surface by which the rotary seal ring is retained;
a second sleeve having a large diameter surface and being located in the opposite side of the process fluid relative to the first sleeve;
a second seal portion comprising a rotary seal ring retained in the large diameter surface of the second sleeve;
a floating ring being located within a fluid chamber between the first seal portion and the second seal portion for reducing a pressure;
a third sleeve being located in the opposite side of the process fluid relative to the second sleeve and supporting a bearing;
a fixed sleeve having an outer diameter surface and an inner diameter surface, the outer diameter surface being fitted with inner diameter surfaces of the first sleeve and the second sleeve and the third sleeve and the inner diameter surface of the fixed sleeve being fitted over the rotary shaft; and
a connecting means being disposed, respectively, in the fixed sleeve and the second sleeve by which the two sleeves are joined relative to each other.
In the shaft seal device of the second invention related to the preferred embodiment, the first seal portion is installed on the fit surface between the first sleeve and the first housing, and the first sleeve is fitted to the fixed sleeve.
The floating ring for reducing pressure is disposed within a fluid chamber between the third housing and the fourth housing, and the floating ring and the housings containing the floating ring are fitted over the first sleeve.
The second sleeve is further fitted to and joined with the fixed sleeve after mounting the second seal portion between the second sleeve and the second housing.
The fifth and the sixth housings inside of which a bearing unit is installed are fitted to the third sleeve, and the third sleeve is fitted to and joined with the fixed sleeve by means of the connecting means. Thus, the first sleeve and the second sleeve are fittingly retained via the fixed sleeve, and the first seal portion and the second seal portion are assembled between the individual sleeves and the housings to be integrated as a whole unit of shaft seal device. Inner diameter surface of the fixed sleeve is further fitted to the rotary shaft to complete the assembly of the shaft seal device onto the machine apparatus.
Therefore, the entire shaft seal device will become compact as an integral unit. Disassembly can also be easily done by disengaging the connecting means, and its total assembly cost will be decreased.
Use of the floating ring for pressure reduction enables it to seal the process fluid with a small number of seals like the first seal portion and the second seal portion. Therefore, the number of seals will be decreased and a structure of the shaft seal device is not only simplified, but also an assembly of the entire device is made easy. Also the entire device can be integrated as a sub-assembled part.